Impartial Narrator

I'm not sure if this is some outdated literary argument or a raging current discussion, or a matter that's already been decided by that community, but I'm having an issue. A colleague of mine wrote a novel (! what a dream come true). Let me say that completing a novel is a major accomplishment. Moreover, allowing it into the hands of near strangers (coworkers) is also very brave. For that, I give the author full kudos.

Also, the book is good. (I admit, I've stopped reading it at this point for the reason below, but this applies to what I've read. I do intend to finish it, probably after I settle this with you all.) The story is exciting, the characters are interesting, and the writing is fine (I don't really know what a pre-edited published novel looks like, so I'm not a good judge of this).

The problem is that the narrator (the story is told in third person) is biased, and it bothers me (so much that I had to stop reading). It got me thinking that maybe I haven't been paying attention and the narrator is always biased. I checked some of the novels I've read recently and it looks like although the narrator definitely has a bias because s/he knows how the story is going to go, they generally let the characters or the story tell the story, and let the reader decide about what's good and bad.

I don't want to make this about my colleagues book, however, because I think it's tremendous that the novel is finished and good in the first place. I'm just wondering what the role of the narrator is.